PHP bug oscommerce always select 1st shipping method

I have a little bug
basically i have 2 shipping options and they are listed in the order below

1. DELIVERY
2. COLLECTION

Conditions of Bug

1. only mobile site affected
2. only if paying with paypal_rest module

Basically the flow is

CHOOSE SHIPPING method i.e DELIVERY or COLLECTION
CHOOSE PAYPAL_REST CARD MODULE and enter payment info which then takes me to
CHECKOUT CONFIRMATION PAGE to confirm order

THE BUG
--------------

Basically when we get to the CONFIRMATION PAGE the SHIPPING METHOD always shows the FIRST METHOD available on shipping page

so even if i choose 2. COLLECTION then after i enter my card details on paypal_rest form and i arrive on the CONFIRMATION PAGE the Shipping Method NEVER says collection it will ALWAYS show DELIVERY.

After investigation its because it is showing the method which is FIRST i.e sort order 1
in this case DELIVERY

if i swap the order then it will show collection BUT not cos i selected it but cos its now no.1 on the list

e.g

1. UPS
2. Hermes
3. Pickup
4. Amazon
5. DPD

so even i chose PIckup or Amazon it doesnt matter it will always jump to (register) as 1. UPS because UPS is on 1st place.

so some bug in either the shipping page the payment page the confirmation page or one of the paypal rest files is causing it to choose the FIRST method.

PLEASE HELP
i can give ftp and if u wanna connect with anydesk we can do this also

NO TIME WASTER

LOOKS LIKE A SESSION ISSUE but no idea